topic 2 - states of matter and mixtures

• strong forces of attraction • don’t move from fixed lattice • not much energy • definite shape • definite volume • can only vibrate in fixed positions • expands slightly when heated

• some forces of attraction • particles move past each other but tend to stick together • more energy than solid • no definite shape • definite volume • move with random motion • expand slightly when heated

• nearly no forces of attraction • free to move • more energy than liquid • no definite shape • no definite volume • move with random motion • when heated, expand or pressure increases

solid -> liquid particles gain energy as substance if heated they vibrate more, weakening forces holding solid together at melting point, particles have enough energy to break free and become a liquid

liquid -> gas particles gain even more energy particles move faster, weakening and breaking bonds holding liquid together at the boiling point, particles break bonds to become a gas

gas -> liquid gas cools and particles no longer have enough energy to overcome forces of attraction bonds form at the boiling point, bonds have formed to become a liquid

liquid -> solid particles have less energy and particles don’t have enough energy to overcome forces of attraction bonds form at the melting point, so many bonds have formed that it is a solig

solid -> gas

gas -> solid

a substance completely made up of a single element or compound

a substance containing more than one compound or there are different elements not part of a single compound

every substance has specific melting and boiling point you can test for purity by comparing the melting point of the sample to the expected if a substance is a mixture, it will melt over a range of temperatures instead of at a sharp melting point

• melting point apparatus - a water bath and a thermometer

separating a liquid from a solution

1) place substance (eg. seawater) in a distillation flask 2) set up apparatus (Bunsen burner heats flask there is a thermometer condenser and beaker) 3) connect the condenser to a cold tap using rubber tubing 4) gradually heat the flask so that the part of the solution with the lowest boiling point will evaporate 5) this vapour passes into the condenser where it cools and condenses back into a liquid 6) it flows and collects in the beaker (if seawater is used, salt is left in the flask)

it is hard to separate liquids with similar boiling points

separating a mixture of liquids

1) place mixture in flask 2) attach a fractionating column and condenser 3) gradually heat the flask, collect the different liquids as they evaporate at different temperatures 4) there is a temperature gradient in the fractionating column so the column is cooler at the top and so the liquids with the higher boiling points will condense and run back down to the flask 5) once the first liquid has been collected, raise the temperature until the next one reaches the top

separating an insoluble solid from a liquid

place filter paper into a funnel and pour mixture into it liquid runs through the paper solid residue is left behind

separating a soluble solid from solution

1) pour solution into an evaporating dish and gently heat so that some water evaporates and the solution becomes more concentrated 2) once it is more concentrated, some crystals should begin to appear 3) remove the dish from the heat and leave the solution to cool 4) filter the crystals out and leave them in a warm place to dry or use a desiccator or a drying oven

contains a chemical which removes water from the surroundings to dry something out

separating a mixture of soluble substances and identifying them